Metro 2033 is free at the moment on Steam and I realised that games based on books and books based on video games are a big hit and miss. Here’s my brief run down:

Games based on books:
Discworld 1 & 2: These were based on the series not on an individual book. The games were epically good fun and stayed true to the series. Would recommend and are free (abandonware).
Metro 2033: Odd. The game starts at the end of the book but it is an FPS so I can understand the need to change it. Overall, the book is better than the game.

Books based on games:
Star Wars Battlefront II - Inferno Squad: Good and introduced the some characters from the game. Could have lived without reading the book though.
Watchdogs - Dark Clouds: Really very good if you gloss over the spelling and grammatical errors.
Battlefield 3: Mixed View on this. It’s good and explains the plot of the game a bit better but in general seems a little too close to the game rather than a spin off.
Battlefield 4: Very good. Builds up an introduction to one of the characters and the story is good.
Myst Reader (3 individual books): Really good and add to the series nicely. Wish they’d make more!
Doom - Knee Deep in the Dead: Avoid like the plague! Reads as if you were playing the book!!